An organic EL (Electroluminescence) display device is represented as an example of a display device. An organic EL display device has an organic light-emitting element (hereinafter, referred to as a light-emitting element) in each of a plurality of pixels formed over a substrate. A light-emitting element possesses a layer (hereinafter, referred to as an EL layer) including an organic compound between a pair of electrodes (cathode and anode) and is driven by supplying a current to the pair of electrodes. A color provided by a light-emitting element is mainly determined by an emission material in an EL layer, and a variety of emission colors can be obtained by appropriately selecting an emission material. Full-color display can be realized by arranging a plurality of light-emitting elements giving different colors over a substrate.
Emission color of a light-emitting element can also be adjusted by utilizing a light-interference effect inside or outside a light-emitting element. For example, Japanese Patent Application Publications No. 2006-302878 and 2006-302879 disclose that a resonance structure is arranged over one electrode of a light-emitting element to resonate emission radiated from the light-emitting element, thereby adjusting emission intensity and emission color.